1. Field of Invention
This invention relates generally to ligation type castration tools and more particularly to a compound lever activated tool for placement of a small continuous elastomeric band on large mature animals for castration.
2. Description of Prior Art
In modern animal husbandry it has become increasingly common, responsive to market demands, to castrate bovine bulls after their maturity rather than during infancy as heretofore has been common. Such castration by ligation has become popular because of the simplicity of the process and the benefits it provides in avoiding undesirable consequences such as microbal infection, insect invasion, excessive bleeding and the like. Ligation type castration of younger animals has been and is accomplished largely by use of small preformed continuous elastic or elastomeric bands because of the economic viability provided by allowing rapid castration processing that can be accomplished by relatively unskilled persons. The small elastic bands are generally placed by a spreading type tool having two elongate arms pivotally interconnected in their medial portions to allow expansion of a band carried at one end portion of the tool against its elastic bias for placement over the scrotal pouch of the animal with subsequent release. This process works well with juvenile animals that do not have a mature testicular structure of larger size, but it has not been viable with larger animals having mature testicular structure such as bovine bulls, as a small preformed elastic band that would contract to a small enough configuration to provide ligation generally can not be expanded sufficiently, either by its nature or by use of common spreading type tools, to allow passage over the larger testicular structure of the mature animal.
This problem has been recognized in the past and a solution presented by the instant inventor's U.S. Pat. No. 4,691,704 issued Sep. 8, 1987 and U.S. Pat. No. 5,188,637 issued Feb. 23, 1993, whereunder a length of elastic surgical tubing is formed in place, tensioned about the orifice of an animal's scrotal pouch and fastened in its tensed condition by a metallic clip. Though this process provides effective ligation castration of larger mature animals and has been accepted about the world, problems still remain with the process. The instant castration tool resolves some of these remaining problems by providing an easily operated castrating tool for large mature animals that allows placement of a small continuous elastic band that is expanded by tensioning for placement and thereafter foreshortened in its tensed condition about the scrotal pouch orifice by a clip to allow its ligation function.
Ligation castration with continuous preformed bands is easier and less complex than the formation of ligation banding in place and has fewer possibilities for mistakes or errors, to provide a process that requires less care and skill on the part of an operator and generally may be more easily accomplished by unskilled workmen without historical familiarity with the process. Elongate type ligation material that is formed in place also allows parameters for tensioning and band fastening by a clip that may be varied, either accidentally or deliberately by an operator, to provide results that are not necessarily uniform or consistent and may vary sufficiently to make the process inoperative or harmful to an animal. Continuous band ligation material has more fixed parameters determined by the nature and configuration of the banding material itself, which are more independent of an operator's activities. The continuous banding material also is generally more durable than the elongate ligation material formed in place and is less expensive and more easily handled than the elongate material. There are therefore various advantages in using preformed continuous band type elastic material for ligation castrating, when the use of such material is possible.
The nature of the ligation castration process with small preformed continuous band elastic material rather defines the limits of the parameters required for the elastic bands usable for such purpose, and especially their relaxed size and elastic properties. Such bands must be small enough to fulfill their ligation purpose of providing sufficient elastic force or bias after placement and fastening about the neck of the scrotal pouch to cause atrophy of the tissue outwardly of the band while yet allowing sufficient expansion upon stretching to permit placement over the scrotal pouch. These conditions require a band of approximately one to two inch diameter with substantial cross-sectional area approximating 0.1 square inch in relaxed condition for natural rubber and varying somewhat, depending upon the elastic nature of other eastomric material from which the band is formed. These parameters generally differ by several fold from the corresponding parameters of continuous elastic castration bands heretofore used for smaller immature animals or bands that are not stretched for placement and the parameters tend to dictate the nature of a tool used for their placement.
Since a continuous ligation band must allow passage of the scrotal pouch and contained testicular structure of an animal to be castrated through the orifice it defines, the instant band because of its small size must be enlarged by stretching to allow placement. The instant invention provides a tool to simply and easily accomplish the stretching of such bands of the required nature to a size and configuration that allows placement without damage to the elastic material. The tool provides a forward yoke supporting the band at two points, with a movable stretching rod communicating with the band at a third point between the first two support points to stretch the band in a triangular configuration for placement. To accomplish its purpose with a band of appropriate physical characteristics, the stretching rod requires substantial force that is provided by an associated compound lever operated tensioning mechanism that allows operation by a multiply smaller applied manual force for ease and simplicity of operation.
The problem of maintaining sufficient elastic tension to provide ligation by a continuous band that expands to create a large enough orifice to allow placement is solved by using a fastening clip to foreshorten the portion of the band about the neck of the animal's scrotal pouch. The foreshortened fastened portion of the tensed band then allows release of the tension created by the tool from both band portions to relax that band portion not extending about the scrotal pouch for removal of the tool. The deformable metallic fastening clip disclosed in my prior U.S. Pat. No. 5,188,637 is effective for fastening the band portion about the scrotal pouch.
The compound lever type operation of the tool provides a secondary benefit of speeding the individual castration process and allowing a single operator to accomplish a greater number of castrations in a given period of time than could be accomplished with various prior tools. In the modern practice of animal husbandry often groups of several hundred animals may be castrated over a short period of time in a continuous operation. With prior tools not providing compound leverage operation, the manual force required by a workman in operating various prior castration tools was often so great, and application of that force sufficiently difficult, that the process was tiring to a workman, and particularly his hand and wrist muscles, to such an extent that the workman's physical ability became a limiting factor in the number of sequential castrations that the workman could accomplish without substantial rest. This problem could be of such extent that it might cause permanent physical damage to a workman. The instant tool resolves this problem by requiring substantially less force that is of such nature that it is not unusually tiring or damaging to a workman to allow continuous operation over lengthy periods of time without adverse physiological effects that may cause injury or work slow down. The tool also may easily be motorized if desired.
My invention lies not in any of these features individually, but rather in the synergistic combination of all of the structures of my tool and steps of my process that necessarily give rise to the results flowing therefrom.